400 MORPHOLOGY. 



(some 150), and have never failed, at least in earlier stages, to extract 

 the embryo-sac uninjured, or at least in such large pieces that there can 

 be no doubt of its existence. Meyen denies it in the Liliacece ; I have 

 already shown * how only most imperfect investigation is to blame for 

 this. Link (El. Phil. Bot. ed. 2. ii. 283.) confounds every thing, because 

 he evidently has made no thorough investigation himself, and therefore, 

 copying Mirbel, Brown, and Brongriiart, understood nothing of what 

 they said. To enumerate all his errors and blunders here, would lead 

 me too far ; every one who knows the subject may readily compare Link 

 and the authors named, and my explanations. 



The observation is surest in Lilium candidum and most of the Or- 

 chidacece, since every cell of the nucleus has a distinct cytoblast here, 

 therefore that cell also which expands to form the embryo-sac. By this 

 means we are enabled always to recognise the tolerably perfect embryo- 

 sac as a simple cell on account of its cytoblast. The demonstration of 

 the embryo- sac is easiest in Phorminm tenax, Amygdalece, Nympha- 

 acece, and some Cucurbitacece, in which it may be exhibited free without 

 much trouble. The form of the embryo-sac varies very much, partly 

 depending on whether the cell which becomes converted into it lies 

 nearest to the chalaza, the middle of the nucleus or the nuclear papilla. 

 Very frequently it originally extends out into a cylindrical cell lying in 

 the axis of the nucleus, which then becomes gradually widened from the 

 summit (the part next the nuclear papilla) downward to the base ; in 

 some families this expansion is confined to the upper part, so that the 

 lower portion appears like a filiform appendage to a large vesicle (Amyg- 

 dalece t CucurbitacecBj Nymphceacece). 



Great differences are manifested in the extent to which the nucleus is 

 displaced by the embryo-sac. Sometimes the cellular tissue in the 

 middle of the nucleus is connected into a closer and firmer ring around 

 the embryo-sac, then usually also possessed of granular contents in this 

 spot : thence the embryo-sac can only expand above and below this 

 region, and thus acquire a lyrate form. In some families it displaces 

 the nucleus very early, even to the extent of leaving only its epithelial 

 layer, the nuclear membrane (membrana nuclei), which may then be 

 readily overlooked (e. g. in the Composite) ; in others, this remnant of 

 the nucleus becomes also displaced, and then, in the perfect seed-bud, 

 the embryo-sac lies free in the cavity of the integuments (e. g. in the 

 Orchidacece) ; in most of the Leguminosce it does not stop here, but the 

 internal integument becomes absorbed, sometimes from above down- 

 ward, sometimes vice versa ; then a remnant of the cellular tissue of the 

 nucleus sometimes remains upon the chalaza as a little conical body, so 

 far as it surrounds the pointed lower extremity of the embryo-sac, e. g. 

 in Phaseolus. In other families, too, a little papillary group of cellular 

 tissue often occurs in the chalaza, which is persistent, and, since the em- 

 bryo-sac displaces the cellular tissue in the circumference, projects as a 

 little cone, clothed by the embryo-sac into its cavity, e. g. in Hedychium. 

 The most remarkable phenomena occur in the Scrophulariacece : here the 

 simple integument is very thick, the micropyle canal very long, and the 

 nucleus a very slender longer or shorter cone, which is sometimes wholly 

 displaced by the embryo-sac. As soon as this happens the apex of it 

 extends out into the micropyle canal, and expands into a sac, displacing 



* Wiegmann's Archiv, 1839, vol. i. p. 256. ; Schleiden, Beitrage zur Botanik, vol. i. 

 p. 40, et seq. 



